The present invention relates to a procedure as defined in the preamble of claim 1 for the transmission of operation control functions in a telecommunication system. In particular, the invention relates to the transmission of operation control functions in a WLL system (WLL, Wireless Local Loop).
WLL means connecting a subscriber to a telephone network via a wireless local loop system. The subscriber interface is formed by using a special terminal device. In principle, the terminal device functions like a mobile station known in itself, but it can be assigned a limited mobility area within which it can work. A wireless local loop system can be implemented using any one of several telecommunication systems known in themselves, such as the GSM network (GSM, Global System for Mobile Communications).
The entire WLL system architecture can be built in different ways Among the possible alternatives are a system solution and an access network solution. The system solution is based on the GSM mobile telephone network known in itself and on the operation of a mobile services switching centre (MSC). The system solution functions as a part of the mobile telephone network, so it can also use the services available in the mobile telephone network, such as the short-message service implemented by a short-message service centre.
The access network solution consists of a local exchange, an access node, base transceiver stations and terminal equipment, all known in themselves. In the WLL system, a method for transmitting operation control functions in the form of short messages has been developed. The access network solution comprises no separate short-message service centre, and therefore the short-message service cannot be utilised.
The object of the present invention is to eliminate the drawback mentioned above. A further object of the invention is to disclose a new type of procedure for transmitting short messages in a WLL system without a short-message service centre.
As for the features characteristic of the invention, reference is made to the claims.
The system of the invention comprises an access node connected via a V5 interface to a local exchange. V5 interfaces (V5.1 and V5.2) are defined in ETSI (European Telecommunications and Standard Institute) standards of the ETS 300 324 and ETS 300 347 series. V5 interfaces allow subscribers belonging to a physically separate access network to be connected using the standard interface of a telephone exchange. In conjunction with the access node there is a user interface which can be used to take care of operation control and maintenance functions. Alternatively, the user interface can be implemented e.g. as a remote session via the local exchange user interface or by providing a separate centralised operation control site from where the operation of both the local exchanges and the access nodes is controlled. The access node is further connected via an Abis interface to the wireless local loop system which connects the terminal equipment to the system. The Abis interface is a standard interface used in the GSM mobile telephone system between a base station controller and a base station. A plurality of terminal devices can be connected to the same access node.
According to the invention, the operation control functions are generated in the access node on the basis of input supplied via the user interface. From the operation control functions, short messages are generated in the access node, which transmits them directly to the terminal device.
As compared with prior art, the present invention provides the advantage that no separate short-message service centre is needed in conjunction with operation control functions sent to a terminal device in the form of short messages.
In a preferred embodiment of the present invention, the transmission of short messages is combined with a call control slave chain. The program blocks participating in the operation control and maintenance of terminal equipment as well as the program block controlling the short-message service consist of master and slave processes. A first process sends a service request to the master of a second process, which in turn starts a slave corresponding to the identifier of the first process. The slave process takes care of providing the service throughout the exchange of messages until, after the service has been terminated, it releases itself and the resources it has engaged. The previously known call control system, used in the access node is based on a corresponding master-slave procedure.
In a preferred embodiment of the present invention, the access node processes the data in the TL and RL layers (TL, Transport Layer; RL, Relay Layer) of the short message. In this respect, the invention differs from prior art in that, in the system solution, only the short-message service centre processes the TP-DATA of the TL layer. TP-DATA is a communication protocol used in a mobile telephone system between a short-message service centre and a mobile station. Correspondingly, the mobile services switching centre only communicates using the RL and CM layers (CM, Connection Management), transmitting TP-DATA untouched to the terminal device.
In a preferred embodiment of the present invention, the connection between the terminal device or subscriber line and the corresponding slave process in the access node is accomplished on the basis of an identifier received from the user interface. The identifier may be the V5 interface subscriber identity code of the terminal device or its IMSI code (IMSI, International Mobile Subscriber Identity).
In a preferred embodiment of the present invention, the operation control functions defined by the user interface are converted in the access node into a form compatible with the terminal device. Different terminal devices may have different software versions, so the access node gets the operation control functions applicable to each software version from a file of operation control functions.
In a preferred embodiment of the present invention, a timed operation control function is not sent as such to the terminal device, but the timing is accomplished in the access node by using a separate timer. Upon the lapse of the length of time set in the timer, the processing of the operation control function is continued normally.
In a preferred embodiment of the present invention, a response to an operation control function sent to the terminal device is expected in the access node. In this case, the slave process responsible for the operation control function remains active until the response function is received.
In a preferred embodiment of the present invention, the identification number of the access node is added to the sender field of the RL layer of the short message. This provides the advantage that messages pertaining to different access nodes are distinguished from each other. The procedure differs from the mobile telephone system, where the sender field contains the number of the short-message service centre.
In a preferred embodiment of the present invention, the access node fills in all the fields required in the short message even if they have no significance. This ensures that the message fulfils the criteria pertaining to a short message.
In a preferred embodiment of the present invention, the operation control function consists of a plurality of short messages. In this case messages related to the same function are transmitted in succession.
In a preferred embodiment of the present invention, the access node releases the resources engaged in the transmission of a short message after receiving an acknowledgement of successful transmission of the operation control function.
In a preferred embodiment of the present invention, the access node sends the operation control function to the terminal device in an encrypted form.
In a preferred embodiment of the present invention, subscriber identification, message encryption and formation of a slave chain in conjunction with the reception of a short message are accomplished in the same way as in the case of a normal call.
In a preferred embodiment of the present invention, the short message sent by the terminal device is decrypted in the access node and the response to the operation control function, is separated from the short message.
In a preferred embodiment of the present invention, the terminal device sends the response to the operation control function in the form of a plurality of short messages. In this case, the assembling of the operation control function is done in the access node.
In a preferred embodiment of the present invention, the channel to be used for short message service is given by the call management in conjunction with subscriber search.
In a preferred embodiment of the present invention, the transmission of the short message is accomplished using the SDCCH signalling channel (SDCCH, Stand-alone Dedicated Control Channel) of the Abis interface. If there is a call going on at the same time, the short message is transmitted using the SACCH signalling channel (SACCH, Slow Associated Control Channel). Similarly, if the terminal device starts call setup in the middle of a short message transmission, the transmission of the message is transferred to the SACCH signalling channel. If the call is terminated during the transmission of a short message, the transmission can be continued either in the SACCH signalling channel or it can be transferred to the SDCCH signalling channel.
In a preferred embodiment of the present invention, the terminal device sends a message to the access node if it has detected an error in the transmission of an operation control function. The error message gives the number code of the error situation. Error messages are sent without encryption. In consequence of the error situation, the access node releases all resources engaged.
In a preferred embodiment of the present invention, the wireless local loop system used is based on a digital mobile communication system, preferably the GSM system.